Good point, Steve, but my plants grow stocky even when they're isolated from wind, like when I put them in my skylights for the winter. Wind is a factor, but I think etoliation is the real culprit. If it were merely wind, what's to stop the plants from just growing all lanky and scrambling over nearby low-lying vegetation? Much of the time, when petiole length increases, the plant effectively becomes shorter, because the leaves don't stand up at all.
~Joe